JP2020091488A - One-side protection polarizing film, polarizing film with adhesive layer and image display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single protective polarizing film having a protective film on only one side of a polarizer and a transparent resin layer on at least one side of the polarizer, which has crack resistance and optical characteristics in a heating and humidifying test. And to keep the bluish tint of the hue small. SOLUTION: This is a single protective polarizing film having a protective film on only one side of a polarizing element, the polarizer has a transparent resin layer on at least one side, and the protective film is provided on at least one side of the polarizer. A feature that is provided through or without a transparent resin layer provided, and that the transparent resin layer contains at least one selected from an inorganic salt of an alkali metal and an inorganic salt of an alkaline earth metal. One-sided protective polarizing film. [Selection diagram] Fig. 1

Description

The present invention relates to a one-sided protective polarizing film having a protective film only on one side of a polarizer. The present invention also relates to a pressure-sensitive adhesive layer-attached polarizing film using the one-sided protective polarizing film. The above-mentioned one-sided protective polarizing film or the polarizing film with a pressure-sensitive adhesive layer may be used alone or as an optical film in which these are laminated to form an image display device such as a liquid crystal display device (LCD) or an organic EL display device.

In the liquid crystal display device, it is indispensable to dispose the polarizing film on both sides of the glass substrate forming the surface of the liquid crystal panel due to its image forming method. As the polarizing film, generally, a polyvinyl alcohol-based film and a polarizer made of a dichroic material such as iodine having a protective film bonded to one or both surfaces thereof with a polyvinyl alcohol-based adhesive or the like are used. ..

In addition, the polarizing film has a problem that cracks are likely to occur in the entire absorption axis direction of the polarizer due to changes in the shrinkage stress of the polarizer in a harsh environment of thermal shock (for example, high temperature test at 95° C. for 250 hours). There is. That is, the polarizing film did not have sufficient crack resistance due to thermal shock under the severe environment. In particular, from the viewpoint of thinning, in the one-sided protective polarizing film provided with the protective film only on one side of the polarizer, the contraction stress of the polarizer on the side provided with the protective film and the contraction of the polarizer on the side opposite to the protective film Due to the difference in stress, excessive stress is generated inside the polarizer, and various cracks tend to occur, from minute cracks of several hundred μm in the absorption axis direction of the polarizer to through cracks that penetrate the entire surface. ..

In order to suppress the occurrence of cracks, for example, a pressure-sensitive adhesive layer-attached polarizing film in which a protective layer having a tensile elastic modulus of 100 MPa or more is provided on a one-sided protective polarizing film, and an adhesive layer is further provided on the protective layer is proposed. (Patent Document 1). In addition, a protective layer made of a cured product of a curable resin composition is provided on one side of a polarizer having a thickness of 25 μm or less, a protective film is provided on the other side of the polarizer, and an adhesive layer is provided outside the protective layer. There has been proposed a polarizing film with a pressure-sensitive adhesive layer, which has (Patent Document 2). The pressure-sensitive adhesive layer-attached polarizing films described in Patent Documents 1 and 2 are effective from the viewpoint of suppressing the occurrence of cracks. Further, from the viewpoint of suppressing the generation of cracks and reducing the thickness and weight, a protective layer made of a water-soluble film-forming composition (polyvinyl alcohol-based resin composition) may be provided on at least one surface of the polarizer. It has been proposed (Patent Document 3).

JP, 2010-009027, A JP, 2013-160775, A JP, 2005-043858, A

According to Patent Documents 1 to 3, the protective layer can suppress the contraction of the front polarizer in the absorption axis direction to some extent, and suppress the occurrence of the crack. For forming the protective layer, for example, a forming material containing a polyvinyl alcohol-based resin is suitable in terms of adhesion to a polarizer, coating stability, productivity, and the like. In particular, in Patent Document 3, a polyvinyl alcohol-based resin includes a water-soluble epoxy resin, a dialdehyde such as glyoxal, an isocyanate, an iron ion, a cobalt ion, a nickel ion, a copper ion, a zinc ion, an aluminum ion, and a zirconium ion. It is described that it is preferable to add a curable component or a crosslinking agent such as metal ions.

However, the protective layer containing a polyvinyl alcohol-based resin has a problem in that the rate of decrease in optical characteristics is large in a heating and humidifying test. In addition, the one-sided protective polarizing film having the protective layer had a problem of bluish color (hue exhibits a bluish hue) in the heating and humidifying test, as compared with the case where the protective layer was not provided. Since the blue voids in the polarizing film are easily visible to the human eye, it is desirable that the hue of the polarizing film is stable.

Further, the suppression of the cracks by the protective layer is better as the film thickness of the protective layer is larger, but as the film thickness of the protective layer is larger, the deterioration rate of the optical characteristics in the heating and humidification test is large, and the tendency of blue voids is observed. Was getting bigger. In addition, thinning has also been performed on polarizers. When the polarizer used for the polarizing film is made thin, the change in shrinkage stress of the polarizer becomes small. However, the thinning of the polarizer itself causes the polarizer to break even with a weaker force than conventional ones, and thus crack resistance was not sufficient even with a thin polarizer.

The present invention has a protective film only on one side of the polarizer, and is a one-sided protective polarizing film having a transparent resin layer on at least one side of the polarizer, having crack resistance, and optical in a heating and humidification test. It is an object of the present invention to provide a one-sided protective polarizing film capable of suppressing deterioration of characteristics and blue color.

Another object of the present invention is to provide a polarizing film with an adhesive layer using the polarizing film. Further, the present invention relates to an image display device having the polarizing film or the polarizing film with an adhesive layer.

As a result of earnest studies, the inventors of the present application have found that the above-mentioned problems can be solved by the following one-sided protective polarizing film, and have reached the present invention.

That is, the present invention is a one-sided protective polarizing film having a protective film only on one side of the polarizer,
At least one surface of the polarizer has a transparent resin layer,
The protective film is provided through or without a transparent resin layer provided on at least one surface of the polarizer, and
The one-sided protective polarizing film, wherein the transparent resin layer contains at least one selected from an inorganic salt of an alkali metal and an inorganic salt of an alkaline earth metal.

In the one-sided protective polarizing film, the inorganic salt is preferably iodide. Furthermore, the iodide is preferably potassium iodide.

In the one-sided protective polarizing film, the ratio of the content (a: ionic strength) of the iodine component contained in the polarizer to the content (b: ionic strength) of the inorganic salt component contained in the transparent resin layer ( It is preferable that b/a) is 0.08 or more.

In the one-sided protective polarizing film, the transparent resin layer is preferably formed of a forming material containing a water-soluble resin. As the water-soluble resin, a polyvinyl alcohol resin is preferable.

In the one-sided protective polarizing film, the transparent resin layer preferably has a thickness of 0.2 μm or more. Further, the transparent resin layer preferably has a thickness of 6 μm or less.

In the one-sided protective polarizing film, it is preferable that the polarizer has a thickness of 15 μm or less.

In the one-sided protective polarizing film, the polarizer has an optical property represented by a single transmittance T and a polarization degree P represented by the following formula P>−(10 ^{0.929T−42.4} −1)×100 (however, T<42.3), and
It is preferably in the range represented by P≧99.9 (however, T≧42.3).

The present invention also relates to a pressure-sensitive adhesive layer-attached polarizing film having the one-sided protective polarizing film and the pressure-sensitive adhesive layer.

The present invention also relates to an image display device having the one-sided protective polarizing film or the polarizing film with an adhesive layer.

In the one-sided protective polarizing film of the present invention, the polarizer is provided with the transparent resin layer, and the transparent resin layer can suppress the occurrence of cracks.

On the other hand, in the one-sided protective polarizing film provided with the transparent resin layer, the transparent resin layer is directly provided on the polarizer. Therefore, in the heating and humidifying test, it was found that the iodine component (iodine, iodide, and further complex thereof) and the potassium component (due to iodide) in the polarizer migrate to the transparent resin layer. Then, it was found that the iodine component and the potassium component transferred to the transparent resin layer caused the deterioration of the optical characteristics of the one-sided protective polarizing film and the generation of blue color.

In the one-sided protective polarizing film of the present invention, the transparent resin layer contains an inorganic salt of an alkali metal and/or an inorganic salt of an alkaline earth metal. The inorganic salt is iodide or a similar compound contained in the polarizer. It is considered that the iodine component or potassium component in the polarizer and the inorganic salt in the transparent resin layer can maintain a certain equilibrium relationship. Therefore, it is considered that the migration of iodine component and potassium component in the polarizer to the transparent resin layer is suppressed. Similarly, it is considered that there is no migration of the inorganic salt in the transparent resin layer into the polarizer. As a result, it is considered that the one-sided protective polarizing film of the present invention can suppress the deterioration of the optical characteristics and the blue color drop in the heating and humidifying test, despite the provision of the transparent resin layer.

Further, the one-sided protective polarizing film of the present invention is suitable when a thin polarizer (for example, a thickness of 15 μm or less) is used. The thin polarizer has a small change in shrinkage stress of the polarizer, but the crack resistance was not sufficient due to the thinning of the polarizer itself. According to the polarizing film of the present invention, even when a thin polarizer is used, since it has the transparent resin layer, crack resistance can be improved.

It is an example of a schematic sectional view of a polarizing film of the present invention. It is an example of a schematic sectional view of a polarizing film of the present invention. It is an example of a schematic sectional view of a polarizing film of the present invention.

The one-sided protective polarizing film 10 of the present invention will be described below with reference to FIGS. 1 to 3. The one-sided protective polarizing film 10 has the protective film 3 only on one side of the polarizer 1, and has the transparent resin layer 2 on at least one side of the polarizer 1. The transparent resin layer 2 is (directly) provided on the polarizer 1. In FIG. 1, the transparent resin layer 2 is provided only on one side of the polarizer 1, and the protective film 3 is provided on the polarizing element 1 on the side where the transparent resin layer 2 is not provided. In FIG. 2, the transparent resin layer 2 is provided on both sides of the polarizer 1, and the protective film 3 is provided on one side of the transparent resin layer 2. In FIG. 3, the transparent resin layer 2 is provided only on one side of the polarizer 1, and the protective film 3 is provided on the transparent resin layer 2 side.

Although not shown, the protective film 3 may be used by laminating two or more sheets. Although not shown, the polarizer 1 or the transparent resin layer 2 and the protective film 3 are laminated via intervening layers such as an adhesive layer, a pressure-sensitive adhesive layer, and an undercoat layer (primer layer). Although not shown, the protective film 3 may be provided with an easy-adhesion layer or subjected to an activation treatment to laminate the easy-adhesion layer and the adhesive layer.

Although not shown, the piece protective polarizing film 10 of the present invention may be provided with an adhesive layer. Furthermore, the pressure-sensitive adhesive layer can be provided with a separator. A surface protective film can be provided on the one-sided protective polarizing film 10 of the present invention.

<Polarizer>
The polarizer is not particularly limited, and various kinds can be used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene/vinyl acetate copolymer partially saponified film, and dichroism of iodine or dichroic dye. Examples thereof include polyene oriented films such as those obtained by adsorbing a substance and uniaxially stretched, polyvinyl alcohol dehydrated products, polyvinyl chloride dehydrochlorinated products, and the like. Among these, a polarizer made of a polyvinyl alcohol film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally 2 to 25 μm.

A polarizer obtained by dying a polyvinyl alcohol film with iodine and uniaxially stretching it can be prepared, for example, by immersing polyvinyl alcohol in an aqueous solution of iodine, dyeing it, and stretching it to 3 to 7 times its original length. If necessary, it can be immersed in an aqueous solution of potassium iodide or the like which may contain boric acid, zinc sulfate, zinc chloride or the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, it is possible to wash the stains and anti-blocking agent on the surface of the polyvinyl alcohol-based film, and by swelling the polyvinyl alcohol-based film, the effect of preventing unevenness such as uneven dyeing is also obtained. is there. Stretching may be performed after dyeing with iodine, stretching while dyeing, or stretching and then dyeing with iodine. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in a water bath.

As the polarizer, a thin polarizer having a thickness of 15 μm or less can be used. The thickness of the polarizer is preferably 12 μm, more preferably 10 μm or less, further preferably 8 μm or less, further preferably 7 μm or less, further preferably 6 μm or less, from the viewpoint of thinning and crack resistance due to thermal shock. On the other hand, the thickness of the polarizer is preferably 2 μm or more, more preferably 3 μm or more. Such a thin polarizer has little thickness unevenness and excellent visibility, and since it has little dimensional change, it has excellent durability against thermal shock.

As a thin polarizer having a thickness of 15 μm or less, typically,
Japanese Patent No. 4751486,
Patent No. 4751481,
Japanese Patent No. 4815544,
Japanese Patent No. 5048120,
Japanese Patent No. 5587517,
International Publication No. 2014/077599 pamphlet,
International Publication 2014/077636 pamphlet,
And the thin polarizing film (polarizer) obtained by the production method described therein.

The polarizer has optical characteristics represented by a single transmittance T and a degree of polarization P of the following formula P>−(10 ^{0.929T−42.4} −1)×100 (where T<42.3) and It is preferable to be configured so as to satisfy the condition of P≧99.9 (however, T≧42.3). The polarizing film configured so as to satisfy the above conditions has the performance uniquely required as a display for a liquid crystal television using a large display element. Specifically, the contrast ratio is 1000:1 or more and the maximum brightness is 500 cd/m ² or more. As another application, for example, it is attached to the viewing side of the organic EL display device.

As the thin polarizing film, among the manufacturing methods including a step of stretching in a laminate state and a step of dyeing, in that it can be stretched at a high magnification and the polarization performance can be improved, Japanese Patent No. 4751486 specification, Patent Those obtained by a production method including a step of stretching in an aqueous solution of boric acid as described in Japanese Patent No. 4751481 and Japanese Patent No. 4815544 are preferable, and particularly those described in Japanese Patent Nos. 4751481 and 4815544 are described. What is obtained by a production method including a step of auxiliary stretching in the air before stretching in a boric acid aqueous solution having a certain amount is preferable. These thin polarizing films can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter, also referred to as PVA-based resin) layer and a stretching resin base material in a laminated state and a dyeing step. According to this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without trouble such as breakage due to stretching because it is supported by the stretching resin base material.

<Resin base material>
As the resin base material (stretching resin base material), the one applied to the production of the thin polarizing film can be used. Various thermoplastic resins can be used as a material for forming the resin base material. Examples of the thermoplastic resin include ester-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins such as norbornene-based resins, olefin-based resins such as polypropylene, polyamide rheo resins, polycarbonate-based resins, and copolymer resins thereof. Can be mentioned. Among these, ester resins are preferable from the viewpoint of ease of production and cost reduction. As the ester-based thermoplastic resin base material, an amorphous ester-based thermoplastic resin base material or a crystalline ester-based thermoplastic resin base material can be used.

The stretching step is preferably performed, for example, so that the total stretching ratio of the PVA-based resin layer is in the range of 3 to 10 times. The total draw ratio is preferably 4 to 8 times, more preferably 5 to 7 times. It is desirable that the total draw ratio be 5 times or more. The stretching step can be performed in the dyeing step and other steps. The above-mentioned total draw ratio refers to the cumulative draw ratio including the draw in those steps, when the draw is accompanied by the steps other than the draw step.

The dyeing step is performed by adsorbing and orienting a dichroic dye or iodine on the PVA-based resin layer. The dyeing process can be performed together with the stretching process. The dyeing step is generally performed by, for example, immersing in the iodine solution for an arbitrary time. As the iodine aqueous solution used as the iodine solution, an aqueous solution containing iodine and an iodine ion by a iodinated compound as a dissolution aid is used. Examples of the iodide compound include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide. Etc. are used. As the iodide compound, potassium iodide is preferable. The iodide compound used in the present invention is the same as above even when used in other steps.

The iodine concentration in the iodine solution is about 0.01 to 10% by weight, preferably 0.02 to 5% by weight, more preferably 0.02 to 0.5% by weight. The iodide compound concentration is preferably about 0.1 to 10% by weight, more preferably 0.2 to 8% by weight. In dyeing with iodine, the temperature of the iodine solution is usually about 20 to 50°C, preferably 25 to 40°C. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.

In addition to the above steps, for example, an insolubilization step, a cross-linking step, a drying (water content adjustment) step, etc. can be performed.

A boron compound is used as a crosslinking agent in the insolubilization step and the crosslinking step. The order of these steps is not particularly limited. The crosslinking step can be performed together with the dyeing step and the stretching step. The insolubilization step and the crosslinking step can be performed multiple times. Examples of the boron compound include boric acid and borax. The boron compound is generally used in the form of an aqueous solution or a water-organic solvent mixed solution. Usually, a boric acid aqueous solution is used. The boric acid concentration of the boric acid aqueous solution is about 1 to 10% by weight, preferably 2 to 7% by weight. In order to impart heat resistance depending on the degree of crosslinking, the boric acid concentration is preferably the above. An iodide compound such as potassium iodide can be contained in the boric acid aqueous solution or the like. When the boric acid aqueous solution contains an iodide compound, the iodide compound concentration is preferably about 0.1 to 10% by weight, more preferably 0.5 to 8% by weight.

As described above, the polarizer is obtained by subjecting a PVA-based resin or the like to a dyeing process or the like. As a result, the polarizer contains iodide such as potassium iodide for adjusting hue and iodine for controlling polarization characteristics. The content of the iodine component (iodine, iodide, and further a complex thereof) and the potassium component (due to iodide) in the polarizer is usually 1 to 10% by weight, preferably 5 to 8% by weight. ..

<Protective film>
The material forming the protective film is preferably one having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like. For example, polyester-based polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose, acrylic-based polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin). Examples thereof include a polymer and a polycarbonate polymer. Further, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene/propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers. , Polyether sulfone-based polymer, polyether ether ketone-based polymer, polyphenylene sulfide-based polymer, vinyl alcohol-based polymer, vinylidene chloride-based polymer, vinyl butyral-based polymer, arylate-based polymer, polyoxymethylene-based polymer, epoxy-based polymer, or the above Blends of polymers and the like are also mentioned as examples of the polymer forming the protective film. These protective films are usually attached to the polarizer with an adhesive layer. The protective film is made of a thermosetting resin such as a (meth)acrylic resin, a urethane resin, an acrylic urethane resin, an epoxy resin, or a silicone resin, or an ultraviolet curable resin, which is applied to the polarizer and cured. It can be formed by

Note that the protective film may contain one or more kinds of any appropriate additive. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment and a coloring agent. The content of the thermoplastic resin in the protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, further preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the protective film is 50% by weight or less, the high transparency originally possessed by the thermoplastic resin may not be sufficiently exhibited.

A retardation film can be used as the protective film. Examples of the retardation film include those having a front surface retardation of 40 nm or more and/or a thickness direction retardation of 80 nm or more. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation film is used as the protective film, the retardation film also functions as a polarizer protective film, so that the thickness can be reduced.

Examples of the retardation film include a birefringent film obtained by uniaxially or biaxially stretching a thermoplastic resin film. The stretching temperature, the stretching ratio, and the like are appropriately set depending on the retardation value, the material of the film, and the thickness.

The thickness of the protective film can be appropriately determined, but generally it is preferably 3 to 200 μm, more preferably 3 to 100 μm in view of workability such as strength and handleability, and thin layer property. Is preferred. In particular, the thickness of the protective film (when the film is previously formed) is preferably 10 to 60 μm, and more preferably 10 to 45 μm from the viewpoint of transportability. On the other hand, the thickness of the protective film (when formed by coating and curing) is preferably 3 to 25 μm, and more preferably 3 to 20 μm from the viewpoint of transportability. The protective film may be used in plural sheets or in plural layers.

A functional layer such as a hard coat layer, an antireflection layer, an antisticking layer, a diffusion layer or an antiglare layer may be provided on the surface of the protective film to which the polarizer is not adhered. The hard coat layer, the antireflection layer, the antisticking layer, the functional layer such as the diffusion layer and the antiglare layer may be provided on the protective film itself, or may be provided separately from the protective film. it can.

<Intervening layer>
The protective film and the polarizer are laminated via intervening layers such as an adhesive layer, a pressure-sensitive adhesive layer, and an undercoat layer (primer layer). At this time, it is desirable that both layers are laminated without an air gap by the intervening layer.

The adhesive layer is formed of an adhesive. The type of adhesive is not particularly limited, and various types can be used. The adhesive layer is not particularly limited as long as it is optically transparent, and various types of adhesives such as water-based, solvent-based, hot melt-based and active energy ray-curable adhesives are used. Alternatively, an active energy ray-curable adhesive is suitable.

Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and water-based polyesters. The water-based adhesive is usually used as an adhesive composed of an aqueous solution, and usually contains 0.5 to 60% by weight of solid content.

The active energy ray-curable adhesive is an adhesive that is cured by active energy rays such as electron beams and ultraviolet rays (radical curable type, cation curable type), and is, for example, an electron beam curable type or an ultraviolet ray curable type. Can be used. As the active energy ray curable adhesive, for example, a photo radical curable adhesive can be used. When the photo-radical curable active energy ray curable adhesive is used as an ultraviolet curable adhesive, the adhesive contains a radical polymerizable compound and a photopolymerization initiator.

The coating method of the adhesive is appropriately selected depending on the viscosity of the adhesive and the desired thickness. Examples of the coating method include a reverse coater, a gravure coater (direct, reverse or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater and the like. In addition, a method such as a dipping method can be appropriately used for coating.

Further, when the water-based adhesive or the like is used, the coating of the adhesive is preferably performed so that the finally formed adhesive layer has a thickness of 30 to 300 nm. The thickness of the adhesive layer is more preferably 60 to 250 nm. On the other hand, when an active energy ray-curable adhesive is used, it is preferable that the adhesive layer has a thickness of 0.1 to 200 μm. The thickness is more preferably 0.5 to 50 μm, still more preferably 0.5 to 10 μm.

When laminating the polarizer and the protective film, an easy-adhesion layer can be provided between the protective film and the adhesive layer. The easy-adhesion layer can be formed of, for example, various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, or the like. These polymer resins can be used alone or in combination of two or more. Further, other additives may be added to form the easily adhesive layer. Specifically, a tackifier, a UV absorber, an antioxidant, a stabilizer such as a heat stabilizer, and the like may be used.

The easy-adhesion layer is usually provided in advance on the protective film, and the easy-adhesion layer side of the protective film and the polarizer are laminated with an adhesive layer. The easy-adhesion layer is formed by applying a material for forming the easy-adhesion layer onto the protective film by a known technique and drying. The material for forming the easy-adhesion layer is usually prepared as a solution diluted to an appropriate concentration in consideration of the thickness after drying and the smoothness of coating. The thickness of the easily adhesive layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and further preferably 0.05 to 1 μm. It should be noted that a plurality of easy-adhesion layers can be provided, but in this case as well, it is preferable that the total thickness of the easy-adhesion layers be within the above range.

The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive. As the pressure-sensitive adhesive, various pressure-sensitive adhesives can be used, for example, rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, vinyl alkyl ether-based pressure-sensitive adhesives, polyvinylpyrrolidone-based pressure-sensitive adhesives, poly-based pressure-sensitive adhesives. Examples thereof include acrylamide-based adhesives and cellulose-based adhesives. An adhesive base polymer is selected according to the type of the adhesive. Among the pressure-sensitive adhesives, an acrylic pressure-sensitive adhesive is preferably used because it has excellent optical transparency, exhibits appropriate wettability, cohesiveness, and adhesive properties of adhesiveness and is excellent in weather resistance and heat resistance. It

The undercoat layer (primer layer) is formed in order to improve the adhesion between the polarizer and the protective film. The material forming the primer layer is not particularly limited as long as it is a material that exhibits a certain degree of strong adhesion to both the base film and the polyvinyl alcohol resin layer. For example, a thermoplastic resin excellent in transparency, thermal stability, stretchability, etc. is used. Examples of the thermoplastic resin include acrylic resins, polyolefin resins, polyester resins, polyvinyl alcohol resins, and mixtures thereof.

<Transparent resin layer>
The transparent resin layer is formed of various forming materials. The transparent resin layer can be formed by applying the above-mentioned forming material to, for example, a polarizer. The transparent resin layer is provided on at least one surface of the polarizer. The thickness of the transparent resin layer is 0.2 μm or more, and the generation of cracks can be suppressed by the transparent resin layer having the thickness. The thickness of the transparent resin layer is preferably 0.4 μm or more, more preferably 0.5 μm or more, and further preferably 0.7 μm or more. On the other hand, the thickness of the transparent resin layer is preferably 6 μm or less, more preferably 5 μm or less, further preferably 3 μm or less, because if the transparent resin layer becomes too thick, the optical reliability and water resistance decrease. ..

As the material for forming the transparent resin layer, for example, polyester resin, polyether resin, polycarbonate resin, polyurethane resin, silicone resin, polyamide resin, polyimide resin, polyvinyl alcohol resin, acrylic resin, etc. Can be mentioned. These resin materials may be used alone or in combination of two or more. The form of the resin may be either water-based or solvent-based.

The resin forming the transparent resin layer is preferably a water-soluble resin. The water-soluble resin is used as an aqueous solution and has good compatibility with the material for forming the polarizer. Typical examples of the water-soluble resin component include polyvinyl alcohol resin, polyacrylic acid, polyacrylamide, methylol melamine resin, methylol urea resin, resol type phenol resin, polyethylene oxide, carboxymethyl cellulose and the like. These may be used alone or in combination. Polyvinyl alcohol resin, polyacrylic acid, and methylolated melamine are preferably used as the resin component. In particular, polyvinyl alcohol-based resin is suitable. The case where a polyvinyl alcohol resin is used will be described below.

Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Examples of the polyvinyl alcohol-based resin include saponified products of a copolymer of vinyl acetate and a monomer having a copolymerizability. When the copolymerizable monomer is ethylene, an ethylene-vinyl alcohol copolymer is obtained. Examples of the copolymerizable monomer include (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, unsaturated carboxylic acids such as (meth)acrylic acid and esters thereof; ethylene, propylene and the like. α-Olefin, (meth)allyl sulfonic acid (soda), sodium sulfonate (monoalkyl malate), sodium disulfonic acid alkyl malate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N- Examples thereof include vinylpyrrolidone derivatives. These polyvinyl alcohol resins can be used alone or in combination of two or more. From the viewpoint of satisfying wet heat resistance and water resistance, polyvinyl alcohol obtained by saponifying polyvinyl acetate is preferable.

The saponification degree of the polyvinyl alcohol resin is, for example, 96 mol% or more. From the viewpoint of satisfying the wet heat resistance and the water resistance, the saponification degree is preferably 99 mol% or more, more preferably 99.3 mol% or more, and further preferably 99.7 mol% or more. The degree of saponification represents the proportion of units actually saponified into vinyl alcohol units among units that can be converted into vinyl alcohol units by saponification, and the residue is a vinyl ester unit. The saponification degree can be determined according to JIS K 6726-1994.

The average degree of polymerization of the polyvinyl alcohol-based resin may be, for example, 500 or more, but from the viewpoint of satisfying wet heat resistance and water resistance, the average degree of polymerization is preferably 1,000 or more, and more preferably 1500 or more. Is preferable, and more preferably 2000 or more. The average degree of polymerization of the polyvinyl alcohol resin is measured according to JIS-K6726.

As the polyvinyl alcohol-based resin, a modified polyvinyl alcohol-based resin having a hydrophilic functional group on the side chain of the polyvinyl alcohol or its copolymer can be used. Examples of the hydrophilic functional group include an acetoacetyl group and a carbonyl group. In addition, a modified polyvinyl alcohol obtained by converting a polyvinyl alcohol resin into an acetal, urethane, ether, graft, or phosphoric ester can be used.

<<Inorganic salt>>
The transparent resin layer of the present invention contains at least one selected from inorganic salts of alkali metals and inorganic salts of alkaline earth metals. Examples of the alkali metal include lithium, sodium and potassium, and examples of the alkaline earth metal include calcium, strontium and barium. On the other hand, examples of the types of inorganic salts include halides (fluorides, chlorides, bromides, iodides, etc.), sulfides, carbonates, sulfates, borates, phosphates, titanates, and the like.

Specific examples of the inorganic salt of an alkali metal of the present invention include lithium carbonate, lithium chloride, lithium sulfide, lithium iodide; sodium iodide, sodium chloride, sodium fluoride, sodium bromide, trisodium phosphate; Sodium acid, sodium carbonate; potassium iodide, potassium chloride and the like can be mentioned.

Further, specific examples of the inorganic salt of alkaline earth metal include, for example, calcium phosphate, calcium chloride, calcium iodide, calcium carbonate, calcium nitrate; strontium iodide, strontium carbonate, strontium titanate, strontium sulfate, strontium chloride; sulfuric acid. Examples thereof include barium, barium carbonate, barium titanate, barium fluoride and the like.

The inorganic salt is preferably an alkali metal inorganic salt, and particularly preferably a potassium salt. On the other hand, with respect to the type of inorganic salt, iodide is preferable. From the above viewpoint, potassium iodide is particularly preferable as the inorganic salt. Iodide, especially potassium iodide, is used in the process of manufacturing a polarizer, is a material contained in the polarizer, and using the same material as the inorganic salt in a transparent resin is The potassium iodide component is preferable in suppressing the migration into the transparent resin layer.

In addition, in Patent Document 3, the inorganic salt is clearly differentiated from a curable component such as a metal ion or a cross-linking agent that forms a protective layer of a polarizer and is blended with a polyvinyl alcohol-based resin. .. The inorganic salt does not crosslink the polyvinyl alcohol-based resin even when blended in the transparent resin layer using the polyvinyl alcohol-based resin. Moreover, even if an organic salt of an alkali metal and/or an organic salt of an alkaline earth metal is used instead of the inorganic salt, the migration of the iodine component in the polarizer to the transparent resin layer can be sufficiently suppressed. Therefore, it is not possible to suppress deterioration of optical characteristics in the heating and humidification test and to suppress blue voids to be small.

The ratio of the inorganic salt in the transparent resin layer is usually preferably in the range of 1 to 25 parts by weight with respect to 100 parts by weight of the transparent resin layer forming material (for example, polyvinyl alcohol resin). The content of the inorganic salt is preferably 2 to 15 parts by weight, more preferably 5 to 15 parts by weight. By increasing the content of the inorganic salt, blue bleeding can be suppressed. Furthermore, the transmittances on the short wavelength side and the long wavelength side are reduced, and deterioration of the polarizer can be suppressed. However, if the content of the inorganic salt is too large, the film formation of the transparent resin layer is impaired and the crack resistance is lowered, which is not preferable. On the other hand, when the content of the inorganic salt is low, it is not preferable in that the optical characteristics in the heating and humidification test are deteriorated and the bluish color is suppressed to be small.

The inorganic salt has an action of suppressing migration of iodine or potassium iodide in the polarizer into the transparent resin. Therefore, it is preferable to determine the content of the inorganic salt in consideration of the content of the iodine component in the polarizer. For example, the ratio (b/a) of the content (a: ionic strength) of the iodine component contained in the polarizer and the content (b: ionic strength) of the inorganic salt component contained in the transparent resin layer is , 0.08 or more is preferably controlled. The ratio (b/a) is preferably 0.08 or more, and more preferably 0.4 or more, from the viewpoint of suppressing blue light leakage of the polarizer. On the other hand, the ratio (b/a) is preferably 2 or less, more preferably 1.2 or less from the viewpoint of crack resistance. The content (a) of the iodine component and the content (b) of the inorganic salt contained in the transparent resin layer, which are used to calculate the ratio (b/a), can be obtained by the measuring method described in Examples. Ionic strength.

The transparent resin layer can be formed from a forming material containing no curable component. For example, it can be formed from a forming material containing the polyvinyl alcohol resin (PVA resin) as a main component.

The forming material containing the polyvinyl alcohol-based resin as a main component may contain a curable component (crosslinking agent) and the like. The proportion of the polyvinyl alcohol resin in the transparent resin layer or the forming material (solid content) is preferably 80% by weight or more, more preferably 90% by weight or more, and further preferably 95% by weight or more. However, it is preferable that the forming material does not contain a curable component (crosslinking agent).

The curable component (crosslinking agent) can be used from the viewpoint of improving water resistance, but the proportion thereof is 20 parts by weight or less, 10 parts by weight or less, and 5 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. The following is preferable.

The forming material is prepared as a solution in which the polyvinyl alcohol resin is dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Among these, it is preferable to use as an aqueous solution using water as a solvent. The concentration of the polyvinyl alcohol-based resin in the forming material (for example, an aqueous solution) is not particularly limited, but is 0.1 to 15% by weight, preferably 0.5 in consideration of coatability and leaving stability. 10 to 10% by weight.

In addition, examples of the additive for the forming material (for example, an aqueous solution) include a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. Further, a coupling agent such as a silane coupling agent and a titanium coupling agent, various tackifiers, an ultraviolet absorber, an antioxidant, a heat stabilizer, a hydrolysis stabilizer, and the like can be added.

The transparent resin layer can be formed by applying the forming material to a polarizer and drying. The forming material is applied so that the thickness after drying is 0.2 μm or more. The coating operation is not particularly limited, and any appropriate method can be adopted. For example, various methods such as a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method and a knife coating method (comma coating method) can be adopted.

The transparent resin layer can be formed by applying the forming material to the other surface (the surface having no protective film) of the polarizer and drying the applied material. It is preferable to apply the forming material so that the thickness after drying is 0.2 μm or more. The coating operation is not particularly limited, and any appropriate method can be adopted. For example, various methods such as a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method and a knife coating method (comma coating method) can be adopted. Usually, the drying temperature is preferably 60 to 120°C, and more preferably 70 to 100°C. The drying time is preferably 10 to 300 seconds, more preferably 20 to 120 seconds.

<Adhesive layer>
An adhesive layer may be provided on the one-sided protective polarizing film to be used as a polarizing film with an adhesive layer. The pressure-sensitive adhesive layer can be provided on the transparent resin layer, the protective film or the polarizer side depending on the form of the one-sided protective polarizing film. A separator may be provided on the pressure-sensitive adhesive layer of the polarizing film with the pressure-sensitive adhesive layer.

An appropriate pressure-sensitive adhesive can be used to form the pressure-sensitive adhesive layer, and the type thereof is not particularly limited. As the adhesive, a rubber adhesive, an acrylic adhesive, a silicone adhesive, a urethane adhesive, a vinyl alkyl ether adhesive, a polyvinyl alcohol adhesive, a polyvinylpyrrolidone adhesive, a polyacrylamide adhesive, Cellulosic adhesives and the like can be mentioned.

Among these pressure-sensitive adhesives, those having excellent optical transparency, exhibiting appropriate wettability, cohesiveness and adhesiveness, and excellent weather resistance and heat resistance are preferably used. Acrylic pressure-sensitive adhesives are preferably used as those exhibiting such characteristics.

As a method for forming a pressure-sensitive adhesive layer, for example, a method of applying the pressure-sensitive adhesive to a release-treated separator or the like, forming a pressure-sensitive adhesive layer by drying and removing a polymerization solvent, and then transferring to a one-sided protective polarizing film, Alternatively, it is prepared by a method of applying the above-mentioned pressure-sensitive adhesive to a one-sided protective polarizing film and drying and removing a polymerization solvent to form a pressure-sensitive adhesive layer on the polarizer. When applying the pressure-sensitive adhesive, one or more solvents other than the polymerization solvent may be newly added as appropriate.

A silicone release liner is preferably used as the release-treated separator. In the step of applying the pressure-sensitive adhesive of the present invention on such a liner and drying it to form a pressure-sensitive adhesive layer, as a method for drying the pressure-sensitive adhesive, an appropriate method can be appropriately adopted depending on the purpose. Preferably, the method of heating and drying the coating film is used. The heating and drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, and particularly preferably 70°C to 170°C. By setting the heating temperature in the above range, a pressure-sensitive adhesive having excellent pressure-sensitive adhesive properties can be obtained.

As the drying time, an appropriate time can be appropriately adopted. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

Various methods are used for forming the pressure-sensitive adhesive layer. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. Examples thereof include extrusion coating method.

The thickness of the pressure-sensitive adhesive layer is not particularly limited and is, for example, about 1 to 100 μm. The thickness is preferably 2 to 50 μm, more preferably 2 to 40 μm, and further preferably 5 to 35 μm.

When the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer may be protected by a release-treated sheet (separator) until practical use.

As the constituent material of the separator, for example, a plastic film such as polyethylene, polypropylene, polyethylene terephthalate, or a polyester film, a porous material such as paper, cloth, or non-woven fabric, a net, a foamed sheet, a metal foil, or a laminate of these is appropriately used. The thin film may be a thin film, but a plastic film is preferably used because of its excellent surface smoothness.

The plastic film is not particularly limited as long as it is a film capable of protecting the pressure-sensitive adhesive layer, and examples thereof include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film and vinyl chloride. Examples thereof include polymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, ethylene-vinyl acetate copolymer films and the like.

The thickness of the separator is usually 5 to 200 μm, preferably about 5 to 100 μm. In the separator, if necessary, a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, release and antifouling treatment with silica powder or the like, coating type, kneading type, vapor deposition type It is also possible to perform antistatic treatment such as. Particularly, by appropriately performing a peeling treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the separator, the peelability from the pressure-sensitive adhesive layer can be further enhanced.

<Surface protection film>
A surface protective film can be provided on the one-sided protective polarizing film. The surface protective film usually has a base film and a pressure-sensitive adhesive layer, and protects the polarizer through the pressure-sensitive adhesive layer.

As the base film of the surface protection film, a film material having isotropic property or close to isotropic property is selected from the viewpoints of inspection property and manageability. Examples of the film material include polyester resins such as polyethylene terephthalate film, cellulose resins, acetate resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and acrylic resins. Examples include transparent polymers such as resins. Of these, polyester resins are preferred. The base film may be used as a laminate of one or two or more film materials, or a stretched product of the film may be used. The thickness of the substrate film is generally 500 μm or less, preferably 10 to 200 μm.

The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer of the surface protection film includes a (meth)acrylic polymer, a silicone-based polymer, polyester, polyurethane, polyamide, polyether, a fluorine-based or rubber-based polymer as a base polymer. Can be appropriately selected and used. From the viewpoint of transparency, weather resistance, heat resistance, etc., an acrylic pressure-sensitive adhesive containing an acrylic polymer as a base polymer is preferable. The thickness (dry film thickness) of the adhesive layer is determined according to the required adhesive force. It is usually about 1 to 100 μm, preferably 5 to 50 μm.

In the surface protective film, a release treatment layer can be provided on the surface of the base film opposite to the surface provided with the pressure-sensitive adhesive layer, using a low-adhesion material such as silicone treatment, long-chain alkyl treatment, or fluorine treatment. ..

<Other optical layers>
The one-sided protective polarizing film of the present invention can be used as an optical film laminated with another optical layer in practical use. Although the optical layer is not particularly limited, for example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including a wave plate such as 1/2 or 1/4), and a viewing angle compensation film. One or two or more optical layers that may be used can be used. In particular, a reflective polarizing film or a semi-transmissive polarizing film obtained by further laminating a reflection plate or a semi-transmissive reflecting plate on the one-sided protective polarizing film of the present invention, an elliptically polarized light obtained by further laminating a retardation plate at the one-sided protective polarizing film. A film or a circularly polarizing film, a wide viewing angle polarizing film obtained by further laminating a viewing angle compensation film on a one-sided protective polarizing film, or a one-sided protective polarizing film obtained by further laminating a brightness improving film on the one-sided protective polarizing film is preferable.

The optical film obtained by laminating the optical layer on the one-sided protective polarizing film can be formed by a method of sequentially laminating separately in a manufacturing process of a liquid crystal display device or the like. It is excellent in stability of quality and assembling work and has an advantage that the manufacturing process of liquid crystal display devices can be improved. Appropriate adhesion means such as an adhesive layer may be used for lamination. In adhering the above-mentioned one-sided protective polarizing film and other optical films, their optical axes can be arranged at appropriate angles according to the intended retardation characteristics and the like.

The one-sided protective polarizing film or optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed in a conventional manner. That is, a liquid crystal display device is generally formed by appropriately assembling a liquid crystal cell, a piece protective polarizing film or an optical film, and optionally a component such as an illumination system and incorporating a drive circuit. Is not particularly limited except that the one-sided protective polarizing film or the optical film according to the present invention is used, and the conventional method can be applied. The liquid crystal cell may be of any type such as IPS type and VA type.

It is possible to form a suitable liquid crystal display device such as a liquid crystal display device in which a single protective polarizing film or an optical film is arranged on one side or both sides of a liquid crystal cell, or a device using a backlight or a reflector in an illumination system. In that case, the one-sided protective polarizing film or the optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When the one-sided protective polarizing film or the optical film is provided on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a diffusion plate, an anti-glare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a back light, and other appropriate components are provided at a proper position in a single layer or Two or more layers can be arranged.

The present invention will be described below with reference to examples, but the present invention is not limited to the examples shown below. In addition, all parts and% in each example are based on weight. Unless otherwise specified below, the room temperature standing condition is 23° C. and 65% RH.

<Production of polarizer>
Amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a water absorption of 0.75% and a Tg of 75° C. was corona-treated on one side of the base material, and the corona-treated surface was treated with polyvinyl chloride. Alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd. An aqueous solution containing the product name "Gosephimmer Z200") in a ratio of 9:1 was applied and dried at 25°C to form a PVA-based resin layer having a thickness of 11 µm, and a laminate was prepared.
The obtained laminate was uniaxially stretched 2.0 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 120° C. (in-air auxiliary stretching treatment).
Next, the laminated body was immersed in an insolubilizing bath having a liquid temperature of 30° C. (boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Then, the polarizing plate was immersed in a dyeing bath having a liquid temperature of 30° C. while adjusting the iodine concentration and the immersion time so that the polarizing plate had a predetermined transmittance. In this example, 0.2 part by weight of iodine was mixed with 100 parts by weight of water, and 1.0 part by weight of potassium iodide was mixed, and the resultant was immersed for 60 seconds in an aqueous iodine solution (dyeing treatment). ..
Then, it was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 30° C. (an aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with 100 parts by weight of water). (Crosslinking treatment).
Then, the laminate was immersed in an aqueous boric acid solution having a liquid temperature of 70° C. (an aqueous solution obtained by mixing 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with 100 parts by weight of water). Meanwhile, uniaxial stretching was performed between rolls having different peripheral speeds in the longitudinal direction (longitudinal direction) so that the total stretching ratio was 5.5 times (underwater stretching treatment).
Then, the laminated body was immersed in a cleaning bath having a liquid temperature of 30° C. (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
As described above, an optical film laminate including a polarizer having a thickness of 5 μm was obtained.

(Preparation of protective film)
Protective film: A (meth)acrylic resin film having a lactone ring structure having a thickness of 40 μm was subjected to corona treatment on the surface for easy adhesion treatment and used.

(Preparation of adhesive applied to protective film)
40 parts by weight of N-hydroxyethylacrylamide (HEAA), 60 parts by weight of acryloylmorpholine (ACMO) and 3 parts by weight of a photoinitiator "IRGACURE 819" (manufactured by BASF) were mixed to prepare an ultraviolet curable adhesive.

(Evaluation method of polyvinyl alcohol resin)
The degree of polymerization and the degree of saponification of the polyvinyl alcohol resin were measured according to JIS K6726.

(Activated energy ray irradiation)
As an active energy ray, visible light (metal halide lamp filled with gallium) Irradiation device: Fusion UV Systems, Inc. Light HAMMER10 Valve: V valve Peak illuminance: 1600 mW/cm ² , integrated irradiation amount 1000/mJ/cm ² (wavelength 380 to 380) 440 nm) was used. In addition, the illuminance of visible light was measured using a Sola-Check system manufactured by Solatell.

Comparative Example 1
<Preparation of one-sided protective polarizing film>
After bonding the protective film on the surface of the polarizing film of the optical film laminate while applying the ultraviolet curable adhesive so that the thickness of the adhesive layer after curing becomes 0.5 μm, the active energy is applied. The line was irradiated to cure the adhesive. Then, the amorphous PET substrate was peeled off to prepare a one-sided protective polarizing film using a thin polarizing film. The optical characteristics of the obtained one-sided protective polarizing film were such that the transmittance was 42.8% and the polarization degree was 99.99%.

Comparative Examples 2 and 3
<Preparation of polyvinyl alcohol-based forming material>
A polyvinyl alcohol resin having a degree of polymerization of 2500 and a degree of saponification of 99.7 mol% was dissolved in pure water to prepare an aqueous solution having a solid content concentration of 4% by weight.

<Preparation of a one-sided protective polarizing film with a transparent resin layer: corresponding to FIG. 1>
On the surface of the polarizing film (polarizer) of the above-mentioned one-sided protective polarizing film (polarizer surface on which no protective film is provided) obtained in Comparative Example 1, the polyvinyl alcohol-based forming material adjusted to 25° C. was used as a wire bar. After coating with a coater to a thickness of 1.2 μm or 3.3 μm, it was dried with hot air at 60° C. for 1 minute to prepare a one-sided protective polarizing film with a transparent resin layer. The optical characteristics of the obtained one-sided protective polarizing film with a transparent resin layer were a transmittance of 42.8% and a polarization degree of 99.99%.

Comparative Example 4
<Preparation of polyvinyl alcohol-based forming material>
100 parts of polyvinyl alcohol resin having a polymerization degree of 2500 and a saponification degree of 99.7 mol% and 1 part of sodium acetate were dissolved in pure water to prepare an aqueous solution having a solid content concentration of 4% by weight.

<Preparation of a one-sided protective polarizing film with a transparent resin layer: corresponding to FIG. 1>
On the surface of the polarizing film (polarizer) of the above-mentioned one-sided protective polarizing film (polarizer surface on which no protective film is provided) obtained in Comparative Example 1, the polyvinyl alcohol-based forming material adjusted to 25° C. was used as a wire bar. After coating with a coater to a thickness of 1.2 μm, it was dried with hot air at 60° C. for 1 minute to prepare a one-sided protective polarizing film with a transparent resin layer. The optical characteristics of the obtained one-sided protective polarizing film with a transparent resin layer were a transmittance of 42.8% and a polarization degree of 99.99%.

Comparative Examples 5-7, Examples 1-15
<Preparation of polyvinyl alcohol-based forming material>
In Comparative Example 4, as shown in Table 1, polyvinyl alcohol having a solid content concentration of 4% by weight was prepared in the same manner as in Comparative Example 4 except that the kind or the blending amount of the additive (organic salt or inorganic salt) was changed. An aqueous resin solution was prepared.

<Preparation of a one-sided protective polarizing film with a transparent resin layer: corresponding to FIG. 1>
On the surface of the polarizing film (polarizer) of the above-mentioned one-sided protective polarizing film (polarizer surface on which no protective film is provided) obtained in Comparative Example 1, the polyvinyl alcohol-based forming material adjusted to 25° C. was used as a wire bar. After coating with a coater so that the thickness after drying was as shown in Table 1, it was dried with hot air at 60° C. for 1 minute to prepare a one-sided protective polarizing film with a transparent resin layer. The optical characteristics of the obtained one-sided protective polarizing film with a transparent resin layer were a transmittance of 42.8% and a polarization degree of 99.99%.

The following evaluations were performed on the one-sided protective polarizing films obtained in the above Comparative Examples and Examples. The results are shown in Table 1. The evaluation was performed on the obtained one-sided protective polarizing film or the polarizing film with an adhesive layer prepared according to the following.

<Preparation of acrylic polymer>
A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was charged to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a condenser. Further, to 100 parts of the monomer mixture (solid content), 0.1 part of 2,2′-azobisisobutyronitrile as a polymerization initiator was charged together with ethyl acetate, and nitrogen gas was introduced while gently stirring. After purging with nitrogen, the liquid temperature in the flask was kept at around 60° C. to carry out a polymerization reaction for 7 hours. Then, ethyl acetate was added to the obtained reaction solution to prepare a solution of an acrylic polymer having a weight average molecular weight of 1.4 million, which was adjusted to a solid content concentration of 30%.

(Preparation of adhesive composition)
To 100 parts of the solid content of the acrylic polymer solution, 0.1 part of trimethylolpropane xylylene diisocyanate (Takenate D110N manufactured by Mitsui Chemicals, Inc.), 0.3 part of dibenzoyl peroxide, and γ-glycidoxy. 0.075 parts of propylmethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KBM-403) was mixed to prepare an acrylic pressure-sensitive adhesive solution.

(Formation of adhesive layer)
Then, the acrylic adhesive solution is uniformly applied to the surface of a polyethylene terephthalate film (separator film) treated with a silicone release agent with a fountain coater, and dried for 2 minutes in an air circulating constant temperature oven at 155°C. Then, an adhesive layer having a thickness of 20 μm was formed on the surface of the separator film.

<Preparation of polarizing film with adhesive layer>
Then, the pressure-sensitive adhesive layer formed on the release-treated surface of the release sheet (separator) was attached to the transparent resin layer (provided that the polarizer side in Comparative Example 1) of the one-sided protective polarizing film obtained in each example. A polarizing film with an adhesive layer was produced.

<Durability: Rate of change in polarization degree (optical reliability test)>
The obtained adhesive-protected piece protective polarizing film was cut into a size of 25 mm×50 mm (50 mm in the absorption axis direction). The pressure-sensitive adhesive protective polarizing film (sample) was placed in a thermo-hygrostat at 85° C./85% RH for 150 hours. The polarization degree of the one-sided protective polarizing film before and after charging was measured using a spectral transmittance measuring device with an integrating sphere (Dot-3c of Murakami Color Research Laboratory),
The change rate of polarization degree (%)=(1-(polarization degree after charging/polarization degree before charging)) was determined.
The degree of polarization P is the transmissivity (parallel transmissivity: Tp) when two sheets of the same polarizing film are superposed such that their transmission axes are parallel to each other, and the transmissivity of both is orthogonal to each other. It is obtained by applying the transmittance (orthogonal transmittance: Tc) in the combined case to the following formula. Polarization degree P(%)={(Tp−Tc)/(Tp+Tc)} ^1/2 ×100
Each transmittance is represented by a Y value which is adjusted by the 2° visual field (C light source) of JIS Z8701 for the luminosity, with 100% of the completely polarized light obtained through the Glan-Teller prism polarizer.
In Table 1, the change rate of the polarization degree is described, and the change rate was judged according to the following criteria.
◯: Change rate of polarization degree is less than 0.4%.
Δ: Change rate of polarization degree is 0.4% or more and less than 0.5%.
X: The change rate of the degree of polarization is 0.5% or more.

<Durability: orthogonal hue (optical reliability test)>
The obtained adhesive-protected piece protective polarizing film was cut into a size of 25 mm×50 mm (50 mm in the absorption axis direction). The pressure-sensitive adhesive protective polarizing film (sample) was placed in a thermo-hygrostat at 85° C./85% RH for 150 hours. The orthogonal a value (red direction) and the orthogonal b value (blue direction) of the adhesive-protected one-sided protective polarizing film before and after injection are measured with a spectral transmittance measuring instrument with an integrating sphere (Dot-3c of Murakami Color Research Laboratory). Was measured.
The orthogonal b value (blue direction) is shown in Table 1, and the judgment was made according to the following criteria.
◯: Orthogonal b-value exceeds -2.4.
B: Orthogonal b value is more than −3 and −2.4 or less.
X: Orthogonal b value is -3 or less.

<Relative Ratio of Content of Inorganic Salt in Transparent Resin Layer and Content of Iodine in Polarizer>
The inorganic salt content in the transparent resin layer and the iodine content in the polarizer were measured by TOF-SIMS (TRIFT V manufactured by ULVAC-PHI) equipped with a gas cluster ion gun.
The conditions for measurement are shown below.
Etching ions; Ar gas cluster ions Irradiated primary ions; Bi ₃ ²⁺
Primary ion acceleration voltage: 30 kV
Measurement polarity; negative ion Observation of depth profile while etching with argon clusters from the transparent resin layer side of the protective film for polarizing film toward the polarizer side,
The iodine component “I ⁻ (m/z 127)” (ionic strength a) derived from the polarizer and the inorganic salt component “ex:KI ₂ ⁻ (m/z 293)” (ionic strength b) derived from the transparent resin layer were respectively used. It extracted and calculated the ratio (b/a).
The inorganic salt component derived from the transparent resin layer is a case where potassium iodide is used as the inorganic component. m/z is a “mass-to-charge ratio” (amount corresponding to a value obtained by dividing atomic weight/molecular weight by electric charge), and KI ₂ ⁻ (m/z 293) was detected as a secondary ion in the inorganic salt component. There is.
The ionic strength b is derived from the following points by the inorganic salt component.
In the case of sodium chloride: Cl ⁻ (m/z 35)
In the case of sodium sulfate and zinc sulfate: SO ₃ ⁻ (m/z 80)
In the case of calcium chloride: Cl ⁻ (m/z 35)

<Crack resistance>
The obtained pressure-sensitive adhesive layer-attached polarizing film was cut into a size of length 400 mm x width 708 mm (absorption axis direction was 400 mm) and length 708 mm x width 400 mm (absorption axis direction was 708 mm), and length 402 mm x width 710 mm x A sample was prepared by laminating both sides of a non-alkali glass having a thickness of 1.3 mm in the direction of crossed Nicols. The sample was placed in an oven at 95° C. for 250 hours and then taken out to visually confirm whether or not a crack had occurred in the pressure-sensitive adhesive layer-attached polarizing film. This test was performed 10 times for each sample, and the number of samples in which cracks were generated was counted and judged according to the following criteria.
◯: 0 sheets.
Δ: 1 to 3 sheets.
X: 4 or more.

From Table 1, it is recognized that the examples have crack resistance and optical reliability and can suppress the bluish hue. In particular, when potassium iodide is used as the inorganic salt (inorganic salt of alkali metal or inorganic salt of alkaline earth metal) contained in the transparent resin layer, compared to other inorganic salts having the same amount of compounding amount. Good effect of suppressing blue spots. Since potassium iodide is a component similar to the potassium component and iodine component contained in the polarizer, it is considered that exudation is most easily suppressed. On the other hand, Comparative Example 1 does not have the transparent resin layer and therefore cannot satisfy the crack resistance. In Comparative Examples 2 and 3, neither organic salt nor inorganic salt was compounded in the transparent resin layer, so that the optical reliability was not sufficient and the bluish hue was not suppressed to a small level. In Comparative Examples 4 and 5, although the transparent resin layer contains an organic salt, it can be seen that the optical reliability is not sufficient. Further, as shown in Comparative Examples 6 and 7, when an inorganic salt such as zinc salt (inorganic salt of alkali metal, inorganic salt other than alkaline earth metal) is used as the inorganic salt, blue bleeding cannot be sufficiently suppressed. .. In addition, since metal ions of an inorganic salt such as a zinc salt have a role of cross-linking the polyvinyl alcohol-based resin of the transparent resin layer, the flexibility tends to be impaired and the crack resistance tends to decrease.

1 Polarizer 2 Transparent resin layer 3 Protective film 10 Single-sided protective polarizing film

Claims (13)

A single protective polarizing film having a protective film only on one surface of a polarizer,
At least one surface of the polarizer has a transparent resin layer,
The protective film is provided via or without a transparent resin layer on at least one surface of the polarizer, and,
The one-sided protective polarizing film, wherein the transparent resin layer contains at least one selected from an inorganic salt of an alkali metal and an inorganic salt of an alkaline earth metal. The one-sided protective polarizing film according to claim 1, wherein the inorganic salt is iodide. The one-sided protective polarizing film according to claim 2, wherein the iodide is potassium iodide. The ratio (b/a) of the content (a: ionic strength) of the iodine component contained in the polarizer and the content (b: ionic strength) of the inorganic salt component contained in the transparent resin layer is 0. 0.08 or more, The piece protection polarizing film in any one of Claims 1-3 characterized by the above-mentioned. The one-sided protective polarizing film according to any one of claims 1 to 4, wherein the transparent resin layer is formed from a forming material containing a water-soluble resin. The one-sided protective polarizing film according to claim 5, wherein the water-soluble resin is a polyvinyl alcohol-based resin. The one-sided protective polarizing film according to any one of claims 1 to 6, wherein the transparent resin layer has a thickness of 0.2 µm or more. The transparent resin layer has a thickness of 6 μm or less, and the one-sided protective polarizing film according to claim 1. The piece protective polarizing film according to claim 1, wherein the polarizer has a thickness of 15 μm or less. The polarizer has optical characteristics represented by a single transmittance T and a degree of polarization P of the following formula P>−(10 ^{0.929T−42.4} −1)×100 (where T<42.3), as well as,
The one-sided protective polarizing film according to any one of claims 1 to 9, which is configured to satisfy the condition of P≧99.9 (where T≧42.3). A polarizing film with a pressure-sensitive adhesive layer, comprising the one-sided protective polarizing film according to claim 1 and a pressure-sensitive adhesive layer. An image display device comprising the one-sided protective polarizing film according to claim 1 or the polarizing film with a pressure-sensitive adhesive layer according to claim 11. It is a manufacturing method of the piece protection polarizing film in any one of Claims 1-10, Comprising:
One-sided protection including a step of forming the transparent resin layer on at least one surface of the polarizer using a forming material containing at least one inorganic salt selected from inorganic salts of alkali metals and inorganic salts of alkaline earth metals. Manufacturing method of polarizing film.